Vacuum bell cap and downflow



' I P. c. KEITH, JR 1,776,589

VACUUM BELL CAP AND DOWNFLOW Spt. 23, 1930.

Filed May 22, 1928 PcvcY ("Kc M1, Av. INVENTOR.

\\ 3-\\ ATTORNEYS.

Patented Sept. 23, 1930 Qumran STATES PATENT OFFICE rnRcY onnrrn, JR, on NEW YORK, N. Y., ASSIGNOR TO THE M. w. KELLOGG COM- PANY, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE VACUUM BELL CAP AND DO'WNFLOW Application filed May 22, 1928 Serial No. 279,729.

. This invention relates to improvements in counter-current fluid contacting devices, and in particular to bell-caps and downflows for use in fractionating towers which are operated under a vacuum.

\ In the prior construction of fractionating towers designed to be operated under a vacuum, the same type of contacting device or bell-cap and downflow has been used as that used when operating at atmospheric or higher pressures. There are many disadvantages in this type of construction when used in vacuum-towers, the chief of which is the back pressure built up in the tower. This back pressure is due to the resistance which the head of liquid upon each plate furnishes to the upward flow of the vapors. The vapors are forced down into the liquid by the bell-cap, pass out from under it, and up through the liquid to the free space above.-

When operating at atmospheric or higher pressures this method of contacting with its resulting back pressure is not-such a great disadvantage. However, when operating under a vacuum it is highly disadvantageous.

Another disadvantage in the prior con-- struction is the positioning of the downflow forms a pipes in such a manner that the liquid has a tendency to run in a channel across the plate thus lowering the contacting value of the bell-caps on each side of the channel. This channeling eflect thus lowers the efliciency of the entire apparatus as a contacting me- The primary object of the present invention is to provide a construction of the bellcap and downflow pipe which eliminates, among others, the disadvantages stated above. Other objects and advantages got my invention will be apparent from the following description, taken in conjunction with the accompanying drawing, which part of this specification, and in which: Figurel is a side elevation, partially in section,showing the arrangement of the bellcaps and risers on successive plates, the bellcap and riser on the upper plate being shown in vertical section;

gigure 2 is a plan view of the bell-cap; an

Figure 3 is a perspective view of the downflow pipe,

By bringing the vapor or gas into intimate contact with a liquid film, my device eliminates the necessity of forcing .a gas against a liquid head and thus minimizes the back pressure. This is accomplished by passing the gas through a film of liquid as thegas issues from the sides of the bellcap, and an increased contacting surfaceis obtained by using the downflow. pipes as additional contacting instrumentalities.

My device may readily be understood 'by referring more particularly to the drawings, .in which like reference characters denote like parts, and in which 10 denotes a portion of a tray or plate of a bubble tower or similar gas and liquid contacting device,

having a riser 11 surrounding an orifice 12. I

provided with a serrated edge 15 at the bottom, vapor openings 16 positioned below the tray 10, and vapor and liquid overflow openings 17 near the top. A sleeve 18 resting'on the tray, surrounds the riser and downflow pipe. It has a notched bottom 19 to allow free passage of liquid and extends above the liquid level 20. The diameter is such that' there is a channel 29 allowing free flow between the sleeve and the riser and downflow pipe. The sleeve is held in position by the lugs 21, Figure 3, extending from the downflow pipe 13. A bell-cap 22'is placed over the downflow pipe and sleeve and is sup-. ported upon the downflow pipe 13 by means of the projecting lugs 23. On the top of the bell-cap there is a depression 24 which holds' a pool of liquid directed there by the next higher downflow pipe 13. The edge of the bell-cap is below the liquid level 20 and is provided with notches 25 as is usual to obtain an optimum diffusion of gas in the liquid. However, in my bell-cap, the notches 25 extend above the liquid level. Moreover, the side of the bell-cap is provided with embossments' 26 which form channels 27 leading to the apex of each notch 25. The bellcap is of greater diameter than the sleeve so that there is a free passage 28 for vapors between the sleeve and the interior of the bell-cap.

In operation, the liquid flows from a downflow pipe 13, of an upper plate, into the depression 24 in the top of the bell-cap 22, whichis on the next lower plate. This pool of liquid overflows through the channels 27 and is thus directed over the openings of the notches 25. Here it is contacted with the vapors flowing out through the notches after which it drops into the pool of liquid 20 maintained on each tray. The depth of the liquid upon the tray is determined by the height of the overflows 17 above the tray 10. The sleeve 18 prevents the liquid from traveling directly to the overflow openings 17, and instead directs the liquid down to the tray 10 and then up through the channel 29 to the overflow openings 17. By this means stratification of the liquid upon the tray is prevented and all of the liquid is maintained in motion through the fractionating apparatus. The liquid flows through the overflow openings 17 and runs in a relatively thin film down the interior of the downflow 13. During the period in which the liquid is in the downflow pipe it is further contacted with the vapors flowing upwards through the downflow pipe. The serrated bottom edge 15 of the downflow pipe directs the liquid into a spray thus bringing about further intimate contact with the va pors entering at this point. The liquid drops on to the bell-cap on the next lower tray or plate immediately below the downflow pipe and again repeats the course already described. I

The vapors enter the downflow pipe 13 either through theopening 30 immediately above the bell-cap or through the openings 16, located in the pipe in such a position that vapors are drawn oil from. the upper portion of the vapor space between the trays or plates. In passing up through the downflow pipe. as stated before, they are contacted with the liquid film going down and pass out through the opening 31 or through the overflow openings 17. The vapors are then directed downward by the bell-cap 22 and pass out through the notches 25. Here they are intimately brought in contact with a spray of liquid flowing over the notches 25 .and directed there by the channels 27. The vapors then pass into the vapor space between the plates.

It will be seen from the description that each bell-cap is separately supplied with liquid from a plate above. In this manner the channeling efiect is eliminated and each bellcap is fnade continuously effective.

It is understood, of course, that as many as desired of these bell-caps and downflow pipes as shown assembled in the drawing may be incorporated upon a tray, and as many such trays as desired may be assembled for a fractionating apparatus.

1 have described a specific form of my apparatus, but those skilled in the art will see possible modification, so that I do not wish to be limited by this description and drawing but only by the prior art and the appended claims.

I claim:

1. A vapor and liquid contacting device for use in rectifying columns equipped with horizontal partitions carrying liquid up to a normal level comprising a bell-cap having vapor distributing outlets therein extending above the normal liquid level, and further having means for directing liquid over the outer surface of said bell-cap onto said vapor distributing outlets.

2. A vapor and liquid contacting device for use in a vapor and liquid contacting system having a normal liquid level comprising a bell-cap having vapor distributing outlets extending through said bell-cap above the nor mal liquid level and further having channels in the exterior of'said bell-cap extending upwardly from said vapor distributing outlets and adapted to conduct liquid over the outer surface of said bell-cap ontosaid vapor distributing outlets.

3. A bell-cap having an indented top adapted to contain a pool of liquid, having spaced embossments on the side forming channels, said channels leading from said indented top down the side of said bell-cap, and having vapor outlets at the ends of said channels.

4. A vapor and liquid contacting device for use ina vapor and liquid contacting system having a normal liquid level comprising a bell-cap having vapor distributing outlets extending through said bell-cap and projecting above the normal liquid level, having a. depression at the upper end of said bell-cap, and further having a number of channels in the exterior of said bell-cap extending upwardly from the said vapor distributing outlets, communicating with the said depression and adapted to conduct liquid from the said depression onto said vapor distributing outlets.

5. Avapor and liquid contacting device for use in counter-current contacting columns equipped with horizontal partitions carrying liquid up to a normal level comprising a bellcap having vapor distributing outlets therein projecting above the normal liquid level. and a downflow connection having itsiupper extremity covered by said bell-cap but spaced therefrom and extending downwardly therefrom thru the said partition.

6. A vapor and liquidcontacting device for use in counter-current contacting columns equipped with horizontal partitions carrying liquid up to a normal level comprising a bellcap having'vapor distributing outlets therein projecting above the normal liquid level, a downflow connection having its upper ex tremity covered by said bell-cap but spaced therefrom and extending downwardly therefrom through the said partition and terminating at the lower end in means for subdividing liquid flowing downwardly therethrough.

7. vapor and liquid contacting device for use in counter-current contacting columns equipped with horizontal partitions carrybell-cap having vapor distributing; outlets ing liquid up to a normal level comprisin lng liquid up to a normal level comprising a equipped with horizontal partitions carrying.

bell-cap having vapor distributing outlets therein projecting above the normal liquid level and having means for directing liquid,

flow over the outer surface of said bell-cap onto said vapor distributing outlets and a' downflow connection having its upper extremity covered by said bell-cap but spaced therefrom and extending downwardly therefrom through the said partition having means for evenly distributing, liquid flowing downwardly over the interior surface of said downflow connection,

' 9. A vapor and liquid contacting device 7 for use in counter-current contacting columns equipped with horizontal partitions carrytherein projecting above the normal liquid level and having means for directing liquid flow over .theouter surface of said bell-cap onto said vapor distributing outlets, a downflow connection having its upper extremitycovered by said bell-cap but spaced therefrom and extending downwardly therefrom through the said partition having means for evenly distributing liquid flowing downwardly over the interior surface of said downflow connection which means consists in a number of 'circumferentially and symmetrically" disposed slots at substantially a normal liquid level. A,

10. In a counter-current contacting column equipped with a number of horizontal partitions carrying liquid up to a normal level, liquid and vapor contacting devices comprising bell-caps in spaced relationship to said partitions, said bell-caps having vapor distributingoutlets projecting above the said normal liquid level and having means for directing liquid flow over the outer surface of said bell-cap onto said vapor distributing outlets, downflow pipes the upper ends of which are internalto said bell-caps and extending downwardly through the said partition, a plurality of the said liquid and vapor contacting devices disposed along vertical axes whereby liquid downfiowing through one of said downflow pipes is distributed on to the surface of the bell-cap beneath.

a 11. A liquid and vapor fluid contacting device, comprising a tray adapted to hold a liquid, a tubular means adapted to permit the downflow of liquid from the tray and the upflow of vapor through the tray, a deflecting means surrounding said tubular means but spaced therefrom, said deflecting means ex tending above the liquid level and having its lower portion adapted to permit the free flow of liquid whereby stratification of the liquid is prevented. and a second deflecting means covering said tubular means and said first de-' flecting means but spaced therefrom, said second deflecting means having vapor outlets and a liquid distributing means upon its outer surface whereby liquid is directed over the vapor outlets.

12. A counter-current fluid contacting device comprising a tray adapted to hold a liquid, a riser, a downflow for liquid from the tray and the upfiow of vapor through the tr,ay. a battling means having a notched lower edge surrounding said riser and downflow and extending above theliquid level whereb stratification of the liquid is prevented, a bellcap covering said downflow and bafiiing means but spaced therefrom, said bell-cap having vaporoutlets on the side, said outlets extending above the liquid level and means on said bell-cap for directing liquid over said outlets whereby a contact between vapor and liquid is obtained.

13. A counter-current fluid contacting device comprising a tray adapted to hold a liquid, a riser, a downflow extending through said riser adapted to permit the downflow of liquid from the tray and the upflow of gas or vapor through the tray, and whereby the liquid level is determined, said downflow having a notched lower edge and having apertures at a point below the tray, a battling means having a notched lower edge surrounding said riser and downflow and extending above the liquid 'level whereby Stratification of the liquid is prevented, a bell-cap covering said downflow and bafiiing means but spaced therefrom, said bell-cap having vapor outlets on the side, said outlets extending above the liquid level and means on said bell-cap for directing liquid over said outlets whereby a contact between vapor and liquid is obtained.

14. A vapor and liquid contacting device for use in counter-current columns equipped with horizontal partitions carrying liquid up to a normal level comprising a downflow connection the upper extremity determining the normal liquid level and extending downward- 1y therefrom through the said partition, a baffling means surrounding said downflovv but spaced therefrom extending above the liquid level and adapted at its lower portion to permit the free flow of liquid and a bell-cap covering said baffling means and downflow but spaced therefrom having vapor outlets therein extending above the normal liquidlevel.

15. A vapor and liquid contacting device for use in counter-current columns equipped with horizontal partitions carryingliquid up to a normal level, comprising a dovvnfiow connection the upper extremity determining 4 the normal liquid level and extending downwardly therefrom, through the said partition, a baffling means surrounding said downflow but spaced therefrom extending above the liquid level and adapted at its lower portion to permit the free flow of liquid, a bell-cap covering said baffling means and downflow but spaced therefrom having vapor outlets therein extending above the normal liquid level and channels on the exterior of said bell-cap extending upwardly from said vapor outlets and adapted to conduct liquid over the outer surface of said bell-cap onto the said vapor outlets.

16. In a counter-current contacting column equipped with a number of horizontal partitions carrying liquid up to a normal level, liquid and vapor contacting devices comprising bell-caps in spaced relationship to said partitions, vapor distributing outlets extending through said bell-caps and projecting above the said normal liquid level, means for directing liquid flow over the outer surface of said bell-cap onto said vapor distributing outlets, and means for directing the liquid from a partition onto the bell-caps above the next lower partition.

In testlmony' whereof, I have signed my name to this specification this 18 day of May,

PERCY C. KEITH, JR. 

